Assembling Marble Earth

NASA have a wonderful image of the earth on their website:

http://visibleearth.nasa.gov/view_detail.php?id=7104

However it's split into eight 21,600 by 21,600 pixel jpeg images. This blog post builds the image in nip2.

Download all 8 and load them into nip2:

The tiles join in a simple grid. You can use the Image / Join / Left to Right and Image / Join / Top to Bottom menu items to make a set of pair-wise joins. Click A1 to select it, hold ctrl and click A2 to select that as well and click Image / Join / Top to Bottom. Repeat for all the vertical pairs, then use Left to Right to join those strips to make the final image.

You could also use Image / Join / Array to build the mosaic. This menu item expects a 2D array of images and joins them in the obvious way. In the expression box, enter:

[[A1, A3, A5, A7], [A2, A4, A6, A8]]

To make the 2D array, then click Image / Join / Array to make the same image as above.

You can't save this monster as a jpeg, sadly, since jpeg has a limit of 65535 pixels horizontally or vertically. The best option is probably jpeg-compressed tiled tiff. VIPS format also works well, but of course not many other packages can read it.